The objective of the proposed series of experiments is to map the primate visual system on the basis of conduction velocities of afferent units. Electrodes located in both optic tracts will be used to stimulate nerve fibers which impinge on lateral geniculate nucleus (LGN) and superior colliculus (SC) cells. In addition receptive field characteristics of target cells of the afferent fibers will be recorded with microelectrodes. Correlation of axonal propertiesswith sensory properties of single units will allow one to determine whether specific information channels exist along these different routes. Each SC cell is binocularly driven and recent evidence suggests that intralaminar connections are present in LGN. If specific information channels exist, then they should be demonstrable in the conduction velocities of tectal afferents from both eyes. The question of binocular activation of LGN cells will also be examined with electrical shock stimuli to determine whether the geniculostriate pathway integrates binocular information prior to the cortex. Slight modifications of the above experiments will allow one to determine whether inputs to the LGN and SC are branches of the same cells or constitute separate populations of fibers. Specialized pathways should also be susceptible to early visual deprivation. Moreover, species of monkeys lacking color vison should show a reduced number of channels. Measurements of conduction velocity of retinal afferents of animals raised in mochchromatic light and in nocturnal monochromats will be made.